December 25, 2025
15% faster, 150% spicier
Python 3.15's interpreter for Windows should be 15% faster
Windows Python gets a 15% turbo; Mac sees a bump—and the comments go wild
TLDR: Python 3.15 may make Windows run Python roughly 15% faster, with a smaller boost on Mac. Commenters argue over AI auto-optimizing the core, lament “low-hanging fruit” wasted energy, and nitpick missing links and RSS—equal parts excitement, skepticism, and classic internet chaos.
Python’s next big promise: the Windows version of Python 3.15 could run about 15% faster, with macOS on Apple chips getting a modest 5% boost. The dev behind it partially retracts an earlier apology after fixing compiler issues and warns it might change later—cue the comment wars. One camp is hyped: “Speed me up, baby.” Another is suspicious: “Undocumented compiler tricks? What could go wrong.” A pragmatic voice drops a calm TL;DR: the new “tail-calling” style—think each step directly hands off to the next—beats the older jump-around style by a little, not a lot. Meanwhile, the meme brigade shows up with jokes about tail-calls and “call me, maybe.”
The AI crowd chimed in with a plot twist: why not let machine-learning tools auto-tune Python’s core loop? Others rolled their eyes and demanded basics like an RSS feed and proper links. One commenter even found the EuroPython talk link and wished it was in the post. And then came the spicy eco-angle: if this was “low-hanging fruit,” how many watts have we burned worldwide by running slower code? Finally, hardware purists waded in, grumbling that if this matters, shouldn’t the engine be hand-crafted for each chip? Python fans are split between cheering the free speed, poking holes in the hype, and asking for… an RSS button. Classic internet.
Key Points
- •Tail-calling interpreter for CPython shows ~5% geomean speedup on macOS AArch64 with Xcode Clang and ~15% on Windows x86-64 with experimental MSVC.
- •Computed gotos now provide only low single-digit gains over switch-case on modern Clang, reducing their advantage.
- •Clang’s __attribute__((musttail)) enables enforced tail calls, making tail-call threaded interpreters practical in C.
- •“uv” ships Python 3.14 on macOS with tail calling; official Python 3.15 macOS binaries are planned to include it.
- •Windows results rely on undocumented MSVC features, and changes may be reverted during Python 3.15’s development.